Double-acting two-stroke internal-combustion engine



1,632,984 June 21, 1927. w. RIEHM DOUBLE ACTING TWO-STROKE INTERNAL COMBUSTION ENGINE;

Filed Dec. 23. 1926 Patented June 21, 1927.

UNITED STATES 1,632,984 PATENT OFFICE.

WILHELM RIEHM, OF AUGSBURG, GERMANY, ASSIGNOR TO THE FIRM: MASCHINEN- FABBIK AUGSBUBG-NUERNBERG, AKTIENGESELLSCHAFT, OI AUGSZBUBG, GEE- MANY, A CORPORATION OF GERMANY.

DoUBLE ACTlNG TWO-STROKE INTERNAL-COMBUSTION ENGINE.

Application filed December 23, 1926, Serial No. 156,652, and in Germany December 21, 1925.

In constant pressure internal combustion engines, owing to the high combustionand compression-end pressure, it is impossible to avoid, however carefully the piston be packed, a portion of the combustion gases or of the combustion air being blown out at each stroke through the piston rings. In the case of single acting engine, this is not of importance, as the blown out gases escape directly into the crankchamber or into the atmosphere. In the case of double acting two stroke engines with I port scavenging, these gases can escape during the central portion of the piston stroke, on the side of the outlet ports, through the latter into the exhaust or through the scavenging ports into the scavenging air pipe. It has been found however that on the cylinder sides which are not broken by ports the gases deposit the unburnt oil particles which they carry with them in the central annular piston chamber formed between the upper and lower piston rings, so that on this side a layer of deposits is gradually formed which in the course of working increases in thickness, and in that way tends to displace the piston out of its central position. Thus at the side of the cylinder where the ports are located there is produced a stronger pressure of the piston against the interior surface of the cylinder which results in premature wear at this part. The lateral displacement of the piston will also be transmitted to the piston rod, and is thereby liable to cause further difliculties.

According to this invention at the cylinder sides which are not broken by ports, auxiliary ports are provided through which the said combustion gases and theimpurities carried by them can escape in the central position of the piston. These auxiliary. ports are preferably arranged in the central partof the length of the cylinder between the planes of the two sets of ports so that they are not uncovered by thepiston itself, and may be connected with the exhaust silencer in order to avoid an escape of the gases directly into the atmosphere.

A construction according to the invention is illustrated by way of example in the accompanying drawings, in which Figure 1 represents a lon 'itudinal section through the cylinder and iigure 2 a cross sectlon on the line A-;B of Figure 1.

The engine shown is assumed to be a double acting two stroke internal combustion engine, the scavenging air being admitted into the cylinder through the ports a,

and the combustion gases escaping through the outlet ports I), said air admission ports and exhaust ports bein preferably located in a zone extending on y part way around the cylinder circumference, with an imp'erforate cylinder wall portion opposite them when the said ports are uncovered by the piston during operation.

The piston is constituted by the two disc pistons e, and e which are connected together by the central part f. The intermediate space between the two disc pistons is enclosed by a tubular casing g which recedes slightly from the outer circumference of the disc pistons, so that a narrow intermediate space h exists between the tubular casing and the interior surface of the cylinder. At the side of the cylinder opposite to that at which the inlet and outlet ports are located and which side is normally free from ports, according to the invention are provided a number of auxiliary ports 0 communicating by way of a pipe d with the atmosphere or the exhaust; the combustion gases which during the working of the en gine were blown through. the piston rings and enclosed in the space k, can escape through the said auxiliary ports while the piston is passing through its central position. According to requirements, the auxiliary ports a could be arranged in one or more rows. They are preferably arranged in the centre between the rows of scavenging orts, the said auxiliary ports being out o transverse alignment with the admission ports and exhaust ports, and as shown are so located that during operation the'piston is at all times interposed between said auxiliary ports and the admission and exhaust ports.

Claims.

1. In a two stroke cycle internal combustion engine provided with port scavenging, a cylinder, a piston operable therein, said cylinder having scavenging air admission ports and exhaust ports positioned within a zone extending part way around the cylinder circumference, and auxiliary escape ports located without the said admission and exhaust port zone for permitting the escape ports positioned within a zone extending rings during operation,

part way around the cylinder circumference and auxiliary escape ports located without the said admission and exhaust port zone for permitting the escape therethrough of. combustion gases leaking past the piston said auxiliary ports being out of transverse alignment with the admission andexhaust ports of said zone.

3. In a two stroke cycle internal combustion engine provided with ort scavenging a cylinder, a piston opera le therein an carrying piston rings, said cylinder having scavenging air admission ports and exhaust ports positioned within a zone extending part way around the cylindercircumference and auxiliary escape ports located without the said admission and exhaust port zone for permitting the escape therethrough of combustion gases leaking past the piston rings during operation, said auxiliary ports being out of transverse alignment with the admission and exhaust ports of said zone and located to'have the piston at all times interposed between said auxiliary ports'and said air admission ports and exhaust ports.

4. In a two stroke cycle internal combustion engine provided with port scavenging, a cylinder, a piston operable therein and carrying piston rings, said cylinder having scavenging air admission ports and exhaust ports posltioned within a zone extending part way around the cylinder circumference and auxiliary escape ports located without the said admission and exhaust port zone for permitting the escape therethrough of combustion gases leaking past the piston rings during operation, said auxiliary'ports being out of transverse alignme t with the admission and exhaust ports 0 said zone and located to be covered by the piston during its operation at a time when both the admission ports and the exhaust ports are uncovered.

5. In a two stroke cycle internal combustionvengine provided with port scavenging, a cylinder, a piston operable therein, said cylinder having scavenging air admission ports and exhaust ports positioned within a zone extending part way around the cylinder circumference, and auxiliary escape ports located without the said admission and exhaust port zone for ermitting the escape therethrough of comgustion gases leaking past the piston during operation, said auxiliary ports being controlled by the piston durin its operation.

6. E two stroke cycle internal combustlon the exhaust ports being located to be opened prior to the opening of the air admission ports, the cylinder wall opposite said air admission ports being imperforate, there being auxiliary ports within the cylinder wall out of alignment with the said air admission ports and exhaust ports, and adjacent the said imperforate portion of the cylinder wall, said auxiliary ports being 10- cated to be controlled by the said ports bein adapted to permit escape therethrough o combustion gases leaking past the piston adjacent the sald ports dur- In operation.

. A double acting two stroke cycle insaid piston,

ternal combustion engine of the character described comprising a cylinder, a piston operatin therein; having piston rings at each end thereof and an intermediate portion of reduced diameter located between said rings and providing an annular chamber about said piston and between the said piston and the cylinder wall, and means for permitting the discharge of combustion gases forced past the piston rings into the annular chamber about said piston.

8. A double acting two stroke cycle internal combustion engine of the character described, comprising a cylinder, a piston operating therein to provide a combustion space at each end of the cylinder, said cylinder having exhaust ports and scavenging air admission ports in the wall thereof for each said combustion/space, said exhaust ports. and scavenging air admission ports eing arranged about only a portion of the circumference of the cylinder, and adjacent the transverse center'of the cylinder, said piston 'comprisin a disc portion at each end, each of said (I to control the said admission and exhaust ports associated with one of the said combustion spaces, a piston portion of reduced diameter intermediate said two disc portions and providing an annular chamber between said piston and the cylinder wall, said cylisc portions being adapted inder also having auxiliary ports out of exhaust ports; and apiston within said cylinder comprising two spaced disc portions, a central portion of reduced diameter connecting the disc portions, and a tubular casing interposed between the two said disc portions and surrounding the said central portion and of somewhat less diameter than.

the said disc portions to provide an annular chamber intermediate the said disc portions, the disc portions of said cylinder be- 1 ing adapted to control the said air admission and exhaust ports, and auxiliary ports being located for communication with the annular chamber surrounding the reduced portion of the piston, to permit the escape through said auxiliary ports of gas leaking into the said annular chamber past the disc portions.

In testimony whereof I have aifixed'my signature.

DR. WILHELM RIEHM. 

